This project
started in 1997 as a learning exercise for the purpose
of teaching myself AutoCAD. Somehow the
CAD exercise slowly evolved into a series of
CAD models that culminated in the
SolidWorks CAD model seen above and the assortment of
real-world parts seen below. While it's been a wonderful learning
experience, I'm still not sure I will find time to finish
it. In the interest of reducing the time
commitment of finishing this model, I have given serious thought to
revising the design to incorporate oscillating
cylinders. Regardless of the outcome, I
can say it has been thoroughly enjoyable to research,
interpret, document, design, and fabricate the
components you see here.

Various processes have been
employed in the fabrication of the parts. The
plate frames and some of the valve gear components were
laser cut by one of my students from AutoCAD files I generated. The frame
stretcher was milled from the solid using the vertical
slide accessory on my 25 year old Taig lathe. It
was then shaped, as was the buffer beam, by my own hand
with a jeweler's saw and needle files. While I am
fascinated and pleased by the laser cut parts, I am more
proud of the "hand hewn" ones. I have
developed a real appreciation for cutting metal with
hand tools. The wheels were turned on my Atlas
6" lathe from castings made by Locosteam in the U.K.
They are the only commercially
available parts on this model.
I removed more material from the backs of the wheels
than is usual. This was done to give the
impression of older style wheels that were generally of
lighter construction. Because no original drawings exist,
some of the details and dimensions are plausible reconstructions
(based on research of better documented Crampton types).
Some license has been taken in certain areas in the
interest of operability. Overall though, the proportions
and major dimensions are faithful to the first batch of
Cramptons built by Tulk and Ley in 1846 -1847.

For those of you that have asked
when it will be finished, I must confess that there has
been no progress made in over seven years. At least,
not on the real model. I have,
however, made progress on the CAD model
and have honed my skills on SolidWorks in the process.

UPDATE March, 2015:

The Crampton project was
sold to a modeler in Kansas a few years ago. Its present state of
completion is unknown.

The
chassis is complete,
save a few modifications
to the center
axleboxes. I don't
want any weight resting
on the center axle and
am going to allow it to
"float".

This
eccentric rod is
finished and therefore,
not flat like the
others. I silver
brazed a
"doubler" on
the small end and then
cut the notch with a
small cutter in my Taig
lathe. The
ogee-like curve on the
back of the forked end
was produced by hand
with a needle file.

I
learned
3D CAD
modeling with this
project. The image
above is of a 90%
complete AutoCAD R14
model. While
AutoCAD has some great
3D capabilities, it has
substantial limitations
when changes to the
models and the related
drawings are
required.

Above
is a design study of the
oscillating cylinder
version.
(click image to enlarge)

The
earliest CAD work on
this project was done in
2D and was slow and
painful.
(... I meant to say
educational.)
Mechanical design is an
iterative process and
while 2D CAD facilitates
changes better than the
paper based paradigm it
replaced, it still
leaves much to be
desired.

Modern
parametric CAD tools
such as SolidWorks,
Pro-Engineer, and Inventor
allow for incredible
design flexibility.
In part, this is done by
placing the emphasis on
the creation of geometry
and function.
Modern CAD tools have
evolved from simple
documentation tools, to indispensable
engineering tools where
many possible solutions
may be quickly and
accurately compared and
analyzed prior to making
the first actual
prototype. In the
above model, I was able
to check for
interference and confirm
the accuracy and timing
of the valve events.

I
would encourage anyone that has not yet tried
their hand at cutting metal to jump in. A
jeweler's saw (with lots of high quality spare
blades) and a set of quality needle files is a
relatively small investment. (A small
stock of Band-Aids is equally useful in the
beginning...) Try your hand at cutting
some scraps of 16 gauge brass or steel
sheet. You'll never know where this might
lead unless you try. The potential
rewards are many and varied. Don't let the
lack of a "complete" machine shop stop
you from getting underway. I had convinced
myself that I needed better tools to be able to
start the projects I was interested in.
One book in particular helped me to transcend
the "armchair engineer" phase.
It was J. E. Minns' "Model Railway
Engines". In this book are many fine
examples of beautiful work performed with simple
tools by mere mortals like us. The most
impressive part is that many of the most
beautiful models featured in the book were
created in the latter part of the 19th
century! Desktop CNC equipment was still
over a century away. No more excuses,
start cutting metal!

Michael Martin -
January, 2007

PS If
you find the CAD part of the process
interesting, check out your local community
college for courses.